As many students are facing the issue with homework 2 -question 16 , so I have listed the following reference which would help you to do the problem.

select Publishers name from Table publisher where  Publishers id is equal to (select Titles publishers id from table Titles where length(Title name) = ( select min(length(Title name)) from Titles )); 

As you can see you have to first check for the minimum title name and then match with the publishers id.